Tenebrosa should grow under your conditions - not at it's best, but enough for growing bigger and flowering. When there is a sheath, then you should provide a higher humidity for the best development of the buds.

Tenebrosa should grow under your conditions - not at it's best, but enough for growing bigger and flowering. When there is a sheath, then you should provide a higher humidity for the best development of the buds.

I think so too! I'll find out soon.

One more thing...I've noticed from my readings that tenebrosas growth season is late summer/fall.
Is this correct?

Mine started growing new roots right when I settled it. So I'm expecting a new growth soon.

This means the higher humidity/ higher watering frequency is not in spring or beginning of summer but it's now.
Is this correct?

You have humid microclimates even when it's hot outside. Nestle them among leafy plants.

The room is reaching the limit for the nº of plants.
By other hand I don't want to deal with the restlessness of being constantly monitoring environmental issues and moving plants in and out.
Today I did experiments with wet towels, bowls filled with hot water, even dropped water in hot pans...never got over 40% with the door constantly shut.
That's too much for my patience...

Also, with a humidifier, it will open doors to other genus that I can't grow now so I think it's a good decision.

Bought a humidifier today.
Ultra-sonic system, 5 speed, vapor flow regulator, max capacity of vaporization of 4 l/ 24 hrs, security shut down when the 1,4 l tank is empty, etc.
I will put it to work tomorrow as I'm not at home.
My goal is to maintain an HR=60%.

Update on this one...after using it for a week I'm satisfied.
It runs smoothly, without a noise and I can keep it working for hours in a row.
It takes a while to increase the overal humidity but, while it doesn't happen, I put the plants that need it most under the mist, especially at night.
Outside temps here have been on the low 90's (33ºC today) with a forecast to maintain it for the next 8 days (with some days on the 97 F (36ºC).
Min HR low 20's and high 80's at night.
With these conditions I can increase HR in the growing room from the low 20's to 50-55% (temp between 75~80 F) and keep it during the night which is ok for most of the orchids.

As a side note, after I start to mist my tenebrosa with the humidifier during the day a new growth appeared. I believe these things are connected.

So, I think I made a good choice.

Another side note... It's really boring to keep converting temp units from one system to the other. And it make posts really confusing.